This invention relates to mixtures containing stereoregular polystyrene, in particular isotactic and syndiotactic polystyrene, and solvents for the polystyrene. This invention further relates to a process for the preparation of articles from such stereoregular polystyrene.
Syndiotactic polystyrene is a high performance form of polystyrene. It is desirable to prepare articles from this form of polystyrene. One difficulty in forming such articles is finding solvents for the polystyrene with which to form mixtures which can be used to form articles. Processes and mixtures which can be used to form articles from syndiotactic polystyrene are not known.
In many industries there is a drive to replace the metals used as structural materials with plastic materials. Plastic materials offer several advantages in that they are frequently lighter, do not interfere with magnetic or electrical signals, and often are cheaper than metals. One major disadvantage of plastic materials is that they are significantly weaker than many metals. To provide plastic structural articles and parts which have sufficient strength for the intended use. it is common to use composite materials which comprise a polymer or plastic matrix with high strength fibers in the plastic or polymer matrix to provide enhanced strength. Examples of composites made using such high strength fibers can be found in Harpell et al. U.S. Pat. No. 4,457,985 and Harpell et al. U.S. Pat. No. 4,403,012.
A series of patents have recently issued which relate to high strength fibers of polyethylene, polypropylene or copolymers of polyethylene and polypropylene. Such fibers are demonstrated as being useful in high strength composites. See Harpell et al. U.S. Pat. No. 4,563,392; Kavesh et al. U.S. Pat. No. 4,551,296; Harpell et al. U.S. Pat. No. 4,543,286; Kavesh et al. U.S. Pat. No. 4,536,536; Kavesh et al. U.S. Pat. No. 4,413,110; Harpell et al. U.S. Pat. No. 4,455,273; and Kavesh et al. U.S. Pat. No. 4,356,138. Other polymers which have been used to prepare fibers for composites include polyphenylene sulfide, polyetheretherketone and poly(para-phenylene benzobisthiazole).
The polyethylene and polypropylene fibers although exhibiting excellent modulus and tensile properties, have a relatively low heat distortion temperature and poor solvent resistance. The polyphenylene sulfide, polyetheretherketone, and poly(p-phenylene benzobisthiazole) polymers exhibit excellent heat distortion temperatures and solvent resistance, but are difficult to process and quite expensive.
What is needed is a process for preparing articles from syndiotactic polystyrene or mixtures containing syndiotactic polystyrene. What are also needed are mixtures useful in such processes. What are needed are fibers useful in composites which exhibit good solvent resistance and heat distortion properties are processible, and prepared from materials which have reasonable costs. What are further needed are such fibers with high strength.